Method and device for manufacturing metal tubes by helically coiling a sheet metal strip



BACROIX 4 Sheets-Sheet 1 April 18, 1967 M METHOD AND DEVICE FOR MANUFACTURING METAL TUBES BY HELICALLY COILING A SHEET METAL STRIP IllGd May 8, 1964 M. A. BACROIX April 18, 1967 METHOD AND DEVICE FOR MANUFACTURING METAL TUB BY HELICALLY COILING A SHEET METAL STRIP Filed May 8, 1964 4 Sheets-Sheet z j'hvch 'ok Mfircel Ahare" BAcRo/Y ZAdm-A I A Ho r46 my A ril 18, 1967 A; BACR 3,314,141

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mh'col Andie BACROI X M w31-y I April 18, 1967 M A; BACRCMX 3,314,141

' Filed May a, 1964 METHOD AND DEVICE FOR MANUFACTURING METAL TUBES BY HELICALLY COILING -A SHEET METALSTRIP 4 Sheets-Sheet 4 Vania 1 4h Mu] An duf- 7 EA R'OI X I Mam-14 A fvr'n my United States Patent 3,314,141 METHOD AND DEVICE FOR MANUFACTURING METAL TUBES BY HELICALLY COILING A SHEET METAL STRIP Marcel Andr Bacroix, Pont-a-Mousson, France, assignor to Centre de Recherches d'e Pont-a-Mousson, Meurtheet-Moselle, France, a French body corporate Filed May 8, 1964, Ser. No. 365,947 Claims priority, application France, July 23, 1963, 942,395 9 Claims. (Cl. 29477.3)

The present invention relates to the manufacture of tubes by helically coiling a metal strip and welding the edges of the latter along the contact helix.

The usual method employed for manufacturing tubes of this type includes feeding the metal strip in a direction which is oblique relative to the axis of the tube to be obtained and directly coiling this plane strip within 'a cylindrical tube-forming surface. The edge-to-edge coiling with application of pressure, required by the buttwelding process, can only be obtained if the edges of the strip have a chamfer which permits these two subsequently welded edges or lips to be assembled in the same plane without any tendency to overlap. The weld is efiected at the junction point of the already coiled edge and the edge being coiled. This method employs a ma chine of large size in view of the surface required for feeding the strip obliquely of the coiling axis.

The object of the present invention is to simplify this known technique by the use of a new method which dispenses with the chamfering of the edges of the strip and substantially reduce the overall size of the machines so as to form a straight manufacturing line.

The invention provides a method of manufacturing tubes by helically coiling a sheet metal strip of the type in which the edge of the initially formed coil of the tube and the edge of the coil in the course of formation are buttwelded after being suitably heated. In said method the metal strip having straight edges is fed to the machine in a direction parallel with the coiling axis and, in the course of formation of the tube, each portion of the strip is subjected in succession to the following treating stages: said portion is first so coiled as to impart thereto the shape of a cylindrical portion having the desired radius and generatrices which are oblique relative to the edges of the strip (or oblique relative to the direction of feed of the strip), the angle the generatrices make with the parallel edges of the strip, or initial angle being less than the angle the generatrices of the tube to be obtained make with its coiling helix or final angle; then said initial angle is progressively increased so as to bring it to the value of the final angle by so coiling the metal strip as to form an intermediate portion having the shape of a non-cylindrical developable surface; when the final angle is obtained, the metal strip is coiled a second time at said final coiling angle so as to form a second cylindrical portion at the desired radius and having generatrices parallel with the strip edges before their first coiling (or parallel with the direction of feed of the strip); said coiling is continued so as to form the tube; and finally the adjacent edges of the second cylinder portion and the first coil of the tube are welded.

These coiling or bending operations succeed one another without discontinuity, the intermediate portion having a non-cylindrical developable surface having one generatrix common to said first cylindrical portion and another generatrix common to said second cylindrical portion, said two generatrices making a certain angle there'between.

By means of this method the intermediate portion of non-cylindrical developable surface is progressively Patented Apr. 18, 1967 moved toward the first coil formed of the tube with which it comes into contact when it is transformed into said second cylindrical portion.

Another object of the invention is to provide a machine for carrying out said method. Said machine comprises in combination: -a strip feeding device, a first coiling device oriented obliquely relative to the strip feeding direction, a second coiling device oriented in a direction parallel with the strip feeding direction, said second device being combined with heating means for heating the edges of the strip to be Welded, and means for maintaining said edges of the strip in contact after they have been brought together and strip guiding means located between the two coiling devices and adapted to create a progressive modificationin the orientation of the strip.

Further features and advantages of the invention have been described, many modifications and changes may be made therein with-out departing from the scope of the invention as defined in the appended claims.

In the drawings:

FIG. 1 is a plan view illustrating the method according to the invention;

FIG. 2 is an elevational view taken along line 22 of FIG. 1;

FIG. 3 is a sectional view taken along line 3-3 of FIG. 1;

FIG. 4 is a section of the sheet metal strip employed for forming the tube;

FIG. 5 is a diagrammatic plan view of a machine for carrying out the method according to the invention;

FIG. 6 is a sectional view taken along line 6-6 of FIG. 5;

FIG. 7 is a sectional view taken along line 7--7 of FIG. 5;

FIG. 7a is a view of a detail shown in FIG. 7;

FIG. 8 is a sectional view taken along line 88 of FIG. 5;

FIG. 9 is a diagrammatic sectional view on an enlarged scale of the device for maintaining in contact the adjacent strip edges of the first coil formed and the coil in course of formation;

FIG. 10 is a corresponding view on a smaller scale of a variant of the device for maintaining the edges in contact;

FIG. 11 is a view similar to FIG. 3 of a variant of the method according to the invention.

The method of the invention for manufacturing a tube T from a sheet metal strip t is illustrated in FIGS. 1-4. In this method, a strip T having straight unchamfered edges 1 is employed. This strip T is fed horizontally in a direction AA which is parallel with the axis X--X of the tube T to be formed. This strip is first bent or coiled along generatrices of a cylindrical portion 2, these generatrices being oblique relative to the edges of the strip and consequently relative to the feeding direction AA and preferably making with the latter an initial angle x which is less than the final angle y of that the coiling helix of the formed tube T makes with the generatrices of the latter, The coiling radius of this cylindrical portion 2 is substantially equal to the radius of the tube to be obtained.

After this first oblique coiling and while continuing the coiling of the strip t, its orientation. is modified little by little so as to progressively increase the angle of the coiling helix so as to bring it to the final value y of the helix of the tube T. In this way, a non-cylindrical developable surface portion 3 is formed whose generatrices progressively change direction. This strip 2 is then coiled in a second stage so as to form a cylindrical portion 4 whose generatrices are parallel with the axis XX of the tube T, that is, with the direction of feed AA. The second cylindrical portion 4 is connected to the first cylindrical portion 2 by an intermediate portion 3 having a non-cylindrical developable surface. This intermediate portion 3, whose generatrices pass through the helix of the forward edge of the first coil formed .9, can be conical as shown in the chosen embodiment (FIG. 1), its generatrices therefore intersecting the same point S which is apex of this conical surface. Its first generatrix G1 extending from the apex S and bearing on the helix of the edge of the first coil formed s also pertains to the first cylindrical portion 2 and its last generatrix G2, which intersects the generatrix G1 at S, intersects the edge contact point cor the point at which the adjacent edges of the strip are welded, also pertains to the second cylindrical portion 4. The generatrices G1 and G2 make an angle therebetween equal to the angle x/ y the generatrix G1, and the other generatrices of the cylindrical portion 2 make with the feeding direction AA. Following on the second bending or coiling, the coiling of the strip T is continued at the same coiling angle y as the cylindrical portion 4, thereby producing the tube T.

As is known, the edges of the strip to be welded are heated until they are white hot above the contact point of the strip edges (relative to the helical motion of the strip) for example by circulating an electric current along the edges from extreme points 5 and 6 so that these edges weld together at the contact or abutment point c. The points 5 and 6 are at the same distance from the point c.

The heating conditions for heating the strip edges determine the position of the points 5 and 6 at which the electrodes must be mounted and the distance between these points so that these conditions determine the position of the apex S of the conical portion 3. The latter in fact results geometrically from the value of the angle 566.

An embodiment of a machine according to the invention for carrying out the method just described is shown in FIGS. 5-8.

The machine comprises in combination the following sub-assemblies:

A strip feeding device I.

A device II for the first oblique coiling.

A device III for the second coiling.

An intermediate guide device IV for feeding the strip to the second coiling device.

A heating device V for heating the edges of the strip for example by high frequency (not shown).

A device VI for maintaining the edges of the strip in contact in the welding zone.

I.-The strip feeding device (FIGS. 5 and 6) for feeding the strip t in a direction AA which is parallel with the axis XX of the tube T to be obtained, comprises a table having lower and upper guide rollers 7 mounted in pairs. Disposed on the edges of this guide table are parallel slideways 8 in which the straight edges 1 of the strip t move. A drive device (not shown) feeds this strip and can comprise for example a pair of lower and upper transverse rollers which are in contact with the strip.

II.The device for the first oblique coiling (FIGS. 5 and 6) which forms the first cylindrical portion 2, comprises a stand including a bed 9, a block 10 carrying supporting and bending rollers, a beam 11 carrying countersupport rollers and swan-neck elements 12 carrying a bending plate.

The cylindrical support rollers 13, which are for example three in number, are oriented in the strip feed direction AA. In other words, their horizontal axes are perpendicular to this direction of feed. They are journalled in bearings 14 and 14a (FIGS. 5 and 6) supported by the bed 9 of the stand and by the support block 10. The bending rollers 15 which are for example frustoconical and have vertical axes and are three in number, are aligned in a direction BB which is oblique relative to the feed direction A--A and makes an angle x with the latter. The rollers 15 are carried by the support block 10.

The cylindrical support rollers 13 and the frustoconical bending rollers 15 are located below the strip t.

Cooperating with the cylindrical support rollers 13 and the frustoconical bending rollers 15 are crowned countersupport rollers 16 having a horizontal axis, for example three in number, located above the strip r. These rollers 16 are carried by the support beam 11 which is integral with the support block 10, and their axes are horizontal and preferably perpendicular to the oblique direction BB and concurrent with the axes of the bending rollers 15. To complete this device a bending plate 17 in the form of a concave cylindrical portion is located above the bending rollers 15 and extending in the oblique direction BB.

III.The device for the second coiling (FIGS. 5, 7, 7d) forming the second cylindrical portion 4 and the tube T, comprises a stand including a bed 18, a support block 19 at the input end of the bending device, swan-neck elements 20 and a support block 21.

The support block 19 carries a support roller 22 adapted to support the outer strip edge of the conical portion 3 and of the cylindrical portion 4, that is, the edge opposed to the edge to be welded to the adjacent edge of the first coil formed s. This roller 22 therefore applies said edge to be welded against the edge of the first coil formed s. The roller 22, which is tangent to the edge of the strip at a point located on the generatrix G2, is preferably inclined relative to the horizontal, its axis being parallel with the radius of the tube T intersecting said tangent point. The support block 19 also carries a counter-support roller 23 having a horizontal axis and being internally tangent to the cylindrical portion 4 of the strip on the generatrix G2 so as to guide said strip as it enters under the bending plate 24 carried by the swan-neck elements 20. This plate 24 comprises a concave cylindrical surface corresponding to the outer surface of the tube T. The generatrices of the cylindrical surface of this plate 24 are parallel with the strip feed direction AA. Cooperating with the bending plate 24 are bending rollers 25 having an axis parallel with the axis XX of the tube T. These rollers are carried by the support block 21 and are located on the other side of the bending plate 24 relative to the axis XX of the tube T.

IV.T he intermediate strip coiling device (FIGS. 5 and 8) for bringing the strip to the second coiling device comprises for example a guide plate 26 having a curved shape and constituting internally a casing for the frusto-conical surface portion 3 to be obtained. This guide plate is for example carried by the swan-neck element 20 of the second coiling device and is connected to the cylindrical bending plate 24 along the generatrix G2.

V.The device heating the strip edge is merely represented by the position of the electrodes illustrated by two rectangles 5 and 6 in FIG. 5.

VI.the device for maintaining the strip edges in contact with each other. (FIGS. 5, 7 and 9.) A bed 20a spanning the swan-neck elements 20 has a roller depending therefrom which maintains the strip edges to be welded in contact. This roller has for example a generally cylindrical shape and has a median groove 27a for the passage of a weld bead. It is mounted (-FIG. 7) on a fork 27b which is pivotally mounted at 270 on the bed 20a. The pivot 270 has the same inclination with respect to the horizontal as the radii of the tube T intersecting the generatrix G2. The roller 27 is disposed tangentially with respect to the cylindrical portion 4 of the first coil formed s of the tube T in the zone of the point of contact 0 of the edges to be welded. Owing to the pivot 270, the axis of the roller 27 is oriented orthogonally to the helix of contact of the adjacent strip edges. The bending plate 24 has an opening 28 through which the roller 27 extends.

Operation of the machine The strip T driven by the driving device (not shown) is guided by the rollers 7 and by the lateral slideways 8 of the feed device I in the direction A-A. It is introduced between the rollers 13, 15 and 16. In contact with the rollers 16 it undergoes a first oblique bending or coiling. Thereafter, it is engaged against the oblique bending plate 17 which constitutes a corset which forms with the preceding rollers the first cylindrical portion 2. Between the first and second bending or coiling device the strip progressively modifies its orientation as shown by lthe intermediate conical portion 3. For this purpose, it is guided by the plate 36 which also forms a corset which suitably orients the generatrices, facilitates the engagement of the strip between the bending plate 24 and the roller 23 of the second bending device and permits the strip edge 050 to approach with precision the edge b6c of the first coil formed s.

The strip is thereafter engaged against the roller 22 between the bending plate 24 and the counter-support roller 23. The strip thus undergoes a second bending or coiling and assumes a cylindrical curvature at 4. Thereafter it continues to coil under the effect of the thrust of the feed device. Owing to the action of the bending plate 24 and the rollers 22 and 23, the strip coils round from the generatrix G2 into a cylindrical portion 4 which becomes a coil s of the tube T to be formed.

On the upstream side (relative to the helical motion of the strip) of the contact point of the edge of the cylindrical portion 4 and the edge of the first coil formed s the two adjacent strip edges are heated to white hot by the high frequency heating electrodes and 6. They are heated uniformly throughout their thickness. As the two edges move toward the point of contact c, the angle the generatrices of the conical surface 3 make with the generatrix G2, common to the cylindrical portion 2 and the first coil formed s, decreases and becomes zero at point c.

In the zone of the point 0 the roller 27 maintains the heated strip edges in contact with each other and facilitates the butt-welding thereof in cooperation with the roller 22.

As can be seen, this device operates in a continuous manner and produces a tube T from a plane metal strip t.

Owing to their very similar curvatures on the upstream side (relative to the helical motion of the strip) of the point of contact c, the strip edges meet each other easily in edge-to-edge relation substantially on the same level or in the same plane without any relative sliding therebetween. This permits providing the strip with straight edges and dispensing with chamfers thereon, resulting in a considerable simplification in the preparation of the strips employed in the manufacture of helically wound tubes.

Owing to their straight edges and their similar curvatures near to the point of contact 0, the strip edges to be Welded are heated at 5 and 6 to the same degree and uniformly throughout their thickness and this considerably improves the conditions and the quality of the buttweld obtained at the contact point 0.

Finally, owing to the fact of feeding the strip in the direction A-A parallel with the axis XX of the tube T the overall size of the machine is substantially reduced relative to that of known machines in which the strip is fed in a direction which is oblique to the axis of the tube. A straight manufacturing line is therefore possible with this machine.

Variants Instead of comprising a single roller 27 for maintaining the strip edges in contact with each other the machine can be provided with a pair of outer conical rollers and, if desired, at least one inner roller, such as those described in the French Patent No. 1,303,559 filed on July 31, 1961. FIG. illustrates the use of a pair of frustoconical rollers 29 which are rotatably mounted on a cylindrical head 30 depending from the bed 20a.

In the variant of the method illustrated in FIG. 11 the generatrices G1 and G2 instead of being in the same horizontal plane are in two different horizontal planes owing to a modification in the manner in which the strip is fed and/or in the manner in which the first oblique coiling is efifected. For example, the generatrix G2 is at a lower level than the generatrix G1. In this case, they are not concurrent at the point S but are tangent to a helical curve s The same is true of the intermediate generatrices, such as G3 and G4. All these generatrices tangent to the curve s define an intermediate surface portion connecting the cylindrical portions 2 and 4 which is not conical but helical.

This is the case met with in practice if the dimension H (FIG. 2) is modified between the strip feeding plane and the lower generatrix of the formed tube T, especially when it is increased or when the radius of curvature of the first oblique coiling is increased or when the Weld point 0 is lowered (which amounts to lowering the generatrix G2).

Although specific embodiments of the invention have been described, many modifications and changes may be made therein without departing from the scope of the invention as defined in the appended claims.

Thus the cylindrical plate 17 of the second coiling device and the guide plate 26 for the conical portion 3 can be replaced by any other means such as a series of guide blocks or a series of suitably arranged rollers or both these means combined.

Having now described my invention what I claim as new and desire to secure by Letters Patent is:

1. A method of producing a tube by helically coiling a strip of sheet metal into a series of complete coils which are buttwelded together after having been suitably heated, said method comprising the steps of'feeding the strip which has straight edges to a strip coiling machine in a direction parallel with the axis of the tube and subjecting in the course of formation of the tube each portion of the strip corresponding to a complete coil in the produced tube to the following successive treating stages: initially coiling said portion so as to impart thereto the shape of a cylindrical portion having the desired radius and generatrices which are oblique relative to the edges of the strip, the initial angle that the generatrices make with the parallel edges of the strip being less than the final angle that the generatrices of the tube to be obtained make with the coiling helix of the tube; progressively increasing said initial angle so as to bring it to the value of said final angle by so coiling the strip as to form an intermediate portion having the shape of a non-cylindrica-l developable surface; coiling the strip a second time at said final coiling angle so as to form a second cylindrical portion at the desired radius and having generatrices parallel with the strip edges before their first coiling, continuing said coiling so as to form a complete coil of the tube; and welding the adjacent edges of the second cylindrical portion and the previously-formed complete coil of the tube.

2. A method as claimed in claim 1, wherein the noncylindrical intermediate portion has a generatrix common to the first cylindrical portion and another generatrix common to the second cylindrical portion, said two generatrices making therebetween an angle equal to said initial angle.

3. A method as claimed in claim 2, wherein the two generatrices are concurrent at a point which is the apex of a cone, said intermediate portion being a portion of said cone.

4. A method as claimed in claim 3, wherein the first generatrix of the intermediate conical portion makes with the edges of the latter an angle equal to said initial angle.

5. A machine for producing a tube, comprising in combination a strip feeding device, a first coiling device oriented obliquely relative to the strip feeding direction, a

second coiling device oriented in a direction parallel with the strip feeding direction, said second device being combined with heating means for heating the edges of the strip to be welded, and means for maintaining said edges of the strip in contact after they have been brought together, and strip guiding means located between the two coiling devices and adapted to create a progressive modification in the orientation of the strip.

6. A machine as claimed in claim 5, wherein the first coiling device includes a series of support roller located below the plane of feed of the strip, a series of countersupport rollers located above the plane of feed of the strip, and a series of bending rollers located on the same side of the strip as the support rollers, the rollers of each series being in facing relation and the bending rollers being aligned in a direction which is oblique relative to the sheet feed direction and makes with the latter said initial angle.

7. A machine as claimed in claim 5, wherein the second continuous coiling device includes a cylindrical forming element or corset and, in combination, at least one roller for maintaining the sheet edges to be welded in contact and a pressure-applying roller for applying pressure on the opposite edges and tangent to said edges at a point located on the second generatrix.

8. A machine as claimed in claim 7, wherein the axis of the pressure-applying roller is oriented in a direction corresponding to the radii of the tube which intersectsaid second :generatrix.

9. A machine as claimed in claim 7, wherein the guiding means between the first coiling device and the second coiling device comprises a curved plate connected to said forming element of the second coiling device on a generatrix common to the second cylindrical portion and the non-cylindrical intermediate portion interconnecting the first and second cylindrical portions.

References Cited by the Examiner FOREIGN PATENTS 1,156,042 10 /1963 Germany.

JOHN F. CAMPBELL, Primary Examiner.

L. J. WESTFALL, Assistant Examiner. 

1. A METHOD OF PRODUCING A TUBE BY HELICALLY COILING A STRIP OF SHEET METAL INTO A SERIES OF COMPLETE COILS WHICH ARE BUTTWELDED TOGETHER AFTER HAVING BEEN SUITABLY HEATED, SAID METHOD COMPRISING THE STEPS OF FEEDING THE STRIP WHICH HAS STRAIGHT EDGES TO A STRIP COILING MACHINE IN A DIRECTION PARALLEL WITH THE AXIS OF THE TUBE AND SUBJECTING IN THE COURSE OF FORMATION OF THE TUBE EACH PORTION OF THE STRIP CORRESPONDING TO A COMPLETE COIL IN THE PRODUCED TUBE TO THE FOLLOWING SUCCESSIVE TREATING STAGES: INITIALLY COILING SAID PORTION SO AS TO IMPART THERETO THE SHAPE OF A CYLINDRICAL PORTION HAVING THE DESIRED RADIUS AND GENERATRICES WHICH ARE OBLIQUE RELATIVE TO THE EDGES OF THE STRIP, THE INITIAL ANGLE THAT THE GENERATRICES MAKE WITH THE PARALLEL EDGES OF THE STRIP BEING LESS THAN THE FINAL ANGLE THAT THE GENERATRICES OF THE TUBE TO BE OBTAINED MAKE WITH THE COILING HELIX OF THE TUBE; PROGRESSIVELY INCREASING SAID INITIAL ANGLE SO AS TO BRING IT TO THE VALUE OF SAID FINAL ANGLE BY SO COILING THE STRIP AS TO FORM AN INTERMEDIATE PORTION HAVING THE SHAPE OF A NON-CYLINDRICAL DEVELOPABLE SURFACE; COILING THE STRIP A SECOND TIME AT SAID FINAL COILING ANGLE SO AS TO FORM A SECOND CYLINDRICAL PORTION AT THE DESIRED RADIUS AND HAVING GENERATRICES PARALLEL WITH THE STRIP EDGES BEFORE THEIR FIRST COILING, CONTINUING SAID COILING SO AS TO FORM A COMPLETE COIL OF THE TUBE; AND WELDING THE ADJACENT EDGES OF THE SECOND CYLINDRICAL PORTION AND THE PREVIOUSLY-FORMED COMPLETE COIL OF THE TUBE.
 5. A MACHINE FOR PRODUCING A TUBE, COMPRISING IN COMBINATION A STRIP FEEDING DEVICE, A FIRST COILING DEVICE ORIENTED OBLIQUELY RELATIVE TO THE STRIP FEEDING DIRECTION, A SECOND COILING DEVICE ORIENTED IN A DIRECTION PARALLEL WITH THE STRIP FEEDING DIRECTION, SAID SECOND DEVICE BEING COMBINED WITH HEATING MEANS FOR HEATING THE EDGES OF THE STRIP TO BE WELDED, AND MEANS FOR MAINTAINING SAID EDGES OF THE STRIP IN CONTACT AFTER THEY HAVE BEEN BROUGHT TOGETHER, AND STRIP GUIDING MEANS LOCATED BETWEEN THE TWO COILING DEVICES AND ADAPTED TO CREATE A PROGRESSIVE MODIFICATION IN THE ORIENTATION OF THE STRIP. 